To draw Lewis Structures for polyatomic ions we’ll follow a few simple steps. We first count the number of valence electrons for the polyatomic ion.
Using the Periodic Table we find the number of valence electrons for each element. If the ion has a negative charge (like CN-), we add an additional electron. If it has a positive charge (like NH4 +) we subtract an electron.
We then follow the general process for drawing Lewis Structures (tps://youtu.be/1ZlnzyHahvo).
Not that for polyatomic ions we place brackets around the final Lewis Structure and place the charge on the ion outside of the brackets.
For more complicate Lewis Structures it is also a good idea to check the formal charges (https://youtu.be/vOFAPlq4y_k).
Helpful Videos:
How to Draw Lewis Structures: https://youtu.be/1ZlnzyHahvo
Lewis Structures Practice Video Worksheet: https://youtu.be/DQclmBeIKTc
Determining Formal Charge: https://youtu.be/vOFAPlq4y_k
Formal Charge Practice Video: https://youtu.be/-9f4H0puVzc
Finding Valence Electrons (element): https://youtu.be/x1gdfkvkPTk
Finding Valence Electrons (molecule): https://youtu.be/VBp7mKdcrDk
The Octet Rule: https://youtu.be/6Ecr7m-0E0E
Exceptions to the Octet Rule: https://youtu.be/Dkj-SMBLQzM
Finally the Lewis Structure for SO4 2- is https://youtu.be/lEjQKATnI2A .
